Knob Creek Quarter Oak is the latest limited release in the Knob Creek line. To create Quarter Oak, Beam Suntory ages their standard Knob Creek for a minimum of four years in a quarter cask (13 gallons versus a standard whiskey barrel’s 53 gallon capacity). Then a small amount of this quarter cask aged Knob Creek is blended with standard Knob Creek bourbon to create the final product. Blend ratios were not released by Beam Suntory.